Apparatus for multiple-effect vacuum evaporation.



H. H. DOW. APPARATUS FOR MULTIPLE EFFECT VACUUM EVAPORATION. APPLICATIONFILED DBO. 26,1907

1 94,686. Patented Oct. 5, 1911 2 SHEETS-SHEBT 1.

H. H. DOW. APPARATUS FOR MULTIPLE EFFECT VACUUM EVAPORATION APPLICATIONFILED DEC. 26, 1907.

1,004,686, Patented Oct. 3, 1911.

Z SHEETSSHEET Z.

kg" 992241? f/ ill @TllEi's HERBERT H. DOW, OF MIDLAND, MICHIGAN,MIDLAND, MICHIGAN, A

COMPANY, OF

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ASSIGNOR TO THE DOW CHEMICAL con-Pokemon or MICHIGAN:

APPARATUS FOR MULTIPLE EFFECT VACUUM EVAPORATION.

rooaeee.

Specification of Letters Patent.

Patented Oct. 3, 1911.

Application filed December 26, 1907. Serial No. 408,179.

'Midland, county of Midland. State of Michigan, have invented a-new anduseful Improvement in Apparatus for Multiple- Ellect Vacuum Evaporation,of which the following is a specification, the principle of theinvention being herein explained and the best mode in which I havecontemplated applying that principle, so as to distinguish it from otherinventions.

As indicated, my invention relates to apparatus for evaporation byvacuum process.

Said invention has more particular regard to the improvement ofapparatus of the above class known as multiple ctlect vacuum apparatus,in which the steam arising from the evaporation of a quantityccfsolution thus held under reducedpressure, is employed to heat anadditional quantity of the solution, the object of the invention beingthe provision ofapparatus of this sort that will be simple andeconomical in operation, utilizing a single pump in the production of avacuum in a plurality of chambers.

To the accomplishment of this and related ends said invention, then.consists of the means hereinafter fully described and particularlypointed out in the claims.

The annexed drawings and the following description set forth in detailcertain niechanism embodying the invention, such dis: closed meansconstituting, however. but one of various mechanical forms in which theprinciple of the invention may be used.

In said annexed drawings: Figure 1 represents in more or lessdiagrammatic form, portions appearing in cross section, a plant fordouble elfectvacuum evaporation embodying the several improvementscomprelumdcd in my invention: and Fig. 2 similarly shows apparatusdesigned for triple clleot. evaporation.

The apparatus thus chosen for illustrative PUIPUSQS is primaril designedfor the evaporation of salt brine. but may be used equally well, eitherin its present or in slightly modified form. for the evaporation ofsugar syrup or anv other solution from which it is desired to so] ratethe solid, or for the concentration of liquors from which the Hilld doesnot separate on concentration. The illustrated apparatus isfurthermoredesigned to carry out an improved process in the making ofcrystals from. solutions, particle:

larly salt brine, that forms the subject- Inatter of a co-pendingapplication filed by me November 11. 1907, Serial No. 401,580. Suchapparatus, then, consists essentially of a plurality of open evaportingpans A A, there being two here shown, tho-"second of which is elevatedslightly above-the first so that its liquid contents may be passed on tosaid first pan by gravity. The process of making crystals above referredto involves, .in addition to such flow of the brine, a transfer of thesalt separated from the more highly concentrated solution, in the firstpan to the less highly concentrated solution in the second pan. To thisend the \vall (a of such first pan A. contiguous to the second A isinclined and a conveyer a provided to gather the salt as it settles ontothe bottom and carry the same up such inclined side whence it isdeposited or dropped into the second pan to be carried through thelatter by a corresponding conveyor (L2 operating in such pan. The latterpan has also an inclined discharge end either connected with thesucceeding! pan or with conveying means (not shown). for removing theproduct to any desired point. Suitable connections (1? a respectivelyprovide for a supply of fresh hrinc to pan A, a flow from such secondpan to the first pan A. and a discharge thence oi the highlyconcentrated solution or mother liquor. The heating of the brine in therespective pans is had by mea ns of steam coils u (2 consisting ofsections of pipe disposed longitudinally of the pan and having' theirends suitably connected together. -Steam is supplied to the coils in.

the first pan from any convenient source'in the usual manner; but forthe heating of the second coil the steam derived from the evaporation ofthe contents or" the first pan under vacuum is utilized by means now tobe described.

Elevated above the respective evaporating pans are vacuum chambers ll B,which have ascending pipes 7) 5 for drawing the con-- tents from thecorrcspoiuliat, pans, and descending pipes b o for discharging separatedcrystals. In the apparatusillustrated such discharge is had directlyinto the pan again. but obviously this is immaterial, and, it founddesirable such discharge may be, made into a separate receptacle. as inmy Patent No. 554,916. February 18, 1896. A pipe :3 conducts the steamfrom vacuum charnher B to the steam coil a of the second 1Q gree ofvacuum, while a check valve 7) pre vents any back aid or downwardmovement in pipe 7). It will be observed that the lower ends of pipe 7)and 7f dip below the level of the water in the pans, as does also thelower end of pipe 7) below the level of the water in the tank I). Suchpipe 6", it will be understood, is intended todrain 'away from the coilZfithe condensation formed therein, such tank D forming a water seal andtrap, since the length o't pipe 7) below the coils is made sufficient sothat the vacuum therein may not draw the water in said tank I) up intothe coils, but leave them free to drain into said pipe 7).

llaving thus described with what it is thought, sutlicientdetail thestructure embodied in my improved'type of vacuum apparatus, its methodof operation may be 'briefly set forth. Vhen the apparatus 3O startedand during, its operation, brine is supplied through connection a to.pan it" and thence by connection a to pan A, the rate of such supplybeing so controlled, havmg, due regard to the rapidity of theevaporation, as to leave the mother liquor escaping from dischargepip'c' a of the desiredconcent 'ation. Steam is at the same timeadmitted into the coils at in the first pan the temperature of the brinetherein being 40 raised and held a few degrees above'the boi'ling pointreferred to the vacuum maintained in chamber B. The exhaust pump C isnow set in operation, the valve?) between the ascending pipes 7) b ofthesecond vacuum chamber B'- being temporarily open. Thev immediate effectof such suction accordingly is the production ofv a vacuum in chamber 13corresponding to theheight'ofthe column of liquid from the! point ofjunction of pipe 7) with pipe 7) to the level of the brine'in -pan 1\.Further pumping, by increasing i the vacuum' in chamber B, serves toraise the-c mtents of the pan A into said chamber-Bwithout,however,varying the vacuum in chamber 13,, as will taxevidcnlt'.The level of vessel 1) being sulficiently depressed, a

counter-balancing column of liquid will rise in pipe 7) at the same timethat the vacuum is produced in chamber B in the n'mnncr ust 6 set forth.

'Ttwvill be understood of course that pipe 7) constitutes in ctl'ect abarometric columnhthe'height to which the brine rlses ..in such pipeaneasurnug the degree ot vacuum in chamber it. If a series of This steamcoil is furthermore c0n-' vacuum gages were connected to this pipe atintervals, the one at the top would show the highest vacuum, that at thebottom would show the lowest, and those between woulgL; showintermediate degrees of vacuum. For this reason, if the pipe b (and inthe case of Fig. 2 this remark applies also to pipe If) be tapped intothis barometric column at. any height, the vacuum in said pipe 6", or 71as the case may be, will correspond in degree to that in the barometriccolumn at the point tapped. This will be evident when it is consideredthat the brine in pipe 7) above the junction therewith of said pipe Urests upon such point of junction and diminishes by its weight the totalvacuum in pipe 7). so that the higher-such point of junction with pipe7), the greater the degree of vacuum in pipe 79,- and conversely.thclower the point otcntrance. the lower the degree of vacuum in such pipe71". As a result of the vacuum maintained in heating coils a of thesecond evaporating pan A. the steam "from the low vacuum chamber B isdrawn therein where it heats the brine in such second pan, the water ofcondensation escaping into the pipe 7). V I

The height of the vacuum chamber B and the degree of vacuum maintainedtherein is chosen. both as to its absolute value and its relation to theheight of the chamber 3 and the vacuum maintained therein, so that thetemperature of the vapor coming from B will be sutiicieut to raise thetemperature of the brine in A to above its boiling point under vacuumin: B.

I do notascribenovelty to the utilization of steam derived in thismanner to heat the second cvapo 'ating vessel, but it will be noted thatby means of my apparatus I am enabled to maintain the desired vacuum insuch 'firsti system without the employment of an additional pump, or areducingvalve, as has always been the case heretofore, so fat as I amaware. In other words a single pump connected with the high-vacuumchan'iber is, effective in maintaining" the vacuunr not merely in suchchamber, but also in the low-. vacuum chamber corresponding with thefirst evaporating pan without the introduction of a mechanicallyoperated reducing valve. The simplification. and cheapening otoperationthusaccomplished need not be further dwelt upon. At the. Sametime it will he ol iserved-that aconstant vacuum is may vary withinreasonable limits without harm so long at is. does not thus ati ect thevacuum in such first chamber. As explained in m.v Patent No. 554,916l'iefore'referred to. the How of brine during the operation of pipe 7)up to the point of its I the vacuum evaporator B is up the pipe b anddown Z).

In starting the system, I open valve 5 admitting the air and vapor fromIf to the ascending column of brine, by which itis delivered to thechamber B whence it is drawn out. by the pump. In order to lessen thework of the pump after the system has attained its normal workingcondition, I open the valve Zrgat the same time closing valve (1 thusadmitting thesaid air and vapor from 1) into pipe I), where it is entrained by the descending column ot brine and is carried down into thepan and discharged to the atmosphere by bubblingup through the brinecontained therein.

It should be plainly evident. without fur- -ther delineation than thatshown in Fig.

1, how the double ettcct there illustrated can be extended to triple andhigher multiple effects by suitable adaptation of parts. It has beendeemed advisable. however. to illustrate one such modification, Fig. 2,wherein a triple etl'ect vacuum evapomtion is had. To this end merely athird open heating pan A together with a third vacuum chamber B requireto be employed, these being joined with each other and with the preceding pan A and chamber B of the series by connections correspondingwith those previously described as joining such pan A and chamber B withpan A and chamber I3. These connections have accordingly had applied tothem the same reference characters and their identification thusrendered possible without further description. In this apparatus astheother,

one pump C will sutlice to maintain vacua in all of the evaporator-s,the. degree of vacuum in each being controlled by the correspondingheights at which the pipes 0" if are connected into pipes b b and 5 Inthe same. manner additiona effects ma y be securedas desired or foundadvisable. A.

In this specification, and the claims which follow, the term open asapplied to the heating" vessels is employed to denote that the same areoperated under atmospheric, or substantially atmospheric, pressure, incontradistinction to the prevailing practic in which the liquid beingheated is subjected to reduced pressure during the heating.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the mechanismherein disclosed, provided the mcansstatcd by any one of the followingclaims or the equivalent of such stated means be employed.

l therct'ore particularly point out and distinctly claim as my invention1* l. In apparatus ofthe class described, the combination of two openheating vessels;

vacuum chambers respectively adapted to receive the contents of saidvessels; and'an exhausting device connected with the second of saidchambers for maintaining the desired degree of vacuum therein, saidsecond chamber being connected with said firstchamber so assimultaneously to maintain a vacuum therein. I

In apparatus of the class described, the combination of two open heatingvessels; 'acuum chambers res )ect-ively adapted to receive the contentsoi said vessels; an exhausting device connected with the second of saidchambers for maintaining the desired degree of vacuum therein; and0011-, nections between said two chambers, said connections being soarranged and constructed as simultaneously to maintain a vacuum in saidfirst chamber, but of a lower degree.

3. In apparatus of the class described, the

combination with two open evaporating pans, steam heating devices forsaid pans,

and vacuum chambers respectively adapted I to receive the contentsfiofsaid pans, the heating device of the second pan being con-- nected toreceive steam from the chamber attached to the first pan; of a pump corrnected with the chamber attached'to said second pan for maintaining thedesired degree of vacuum therein, said second chaniher being connectedwith such heating de vice so as simultaneously to maintain a vacuumtherein.

I. In apparatus of the class described, the combination with two openevaporating pans, steam heating devices for said pans, and vacuumchambers respectively adapted to receive the contents of said pans, theheating device of the second pan being connected to receive steam fromthe chamber attached to the first pan; of'a pump connected with thechamber attached to said second pan for maintaining the desired de-.gree of vacuum therein; and connections between said last named chamberand such heating device, said connections being so arranged andconstructed sin'iultaneously to maintain a vacuum in said first namedchamber, but of a lower degree.

5. In apparatus of the class described, the combination of two openevaporating pans; steam heating coils therein; an. elevated vacuumchamber for each of said pans, eachof said. chambers having an ascendingpipe for drawing the contents from the corresponding pan and a desceiiding pipe for discharging separated crystals, tin-: heating coils ofthe second pan beingiconnia' ted to receive steam from the chambercorrespond ingr with the first pan; and a single exhaustinn" deviceadapted simultaneously to create a vacuum in such coils and in thechamber corresponding with said second pan.

(5. In apparatus of the class described, the

&

combination of two open evaporating pans; steam .heating coils therein;an elevated vacuum chamber for each of said pans, each of said chambershaving an ascending pipe for drawing the contents from the correspondingpan and a descending pipe for discharging separated crystals, theheating coils of the second pan being connected to receive steam fromthe chamber corresponding with the first pan; a connection between suchcoils and theascending pipe of the chamber corresponding with saidsecond pan; and a pump connected with said last named chamber formaintaining a vacuum therein.

7. In apparatus of the class described, the combination of two openevaporating pans; steam heating coils therein; an elevated vacuumchamber for each of said pans, each of said chambers having an ascendingpipe for drawing the contents from the corresponding pan and adescending pipe for discharging separated crystals, the heating CO1lS otthe second pan being connectedto receive steam from the chambercorrespond? ing w th the first pan; a connection between such coils andthe ascending pipe of the chamber corres 'iondin'g with said second pan;a valve-controlled pipe adapted. to connect the descending pipe of saidlast named chamber with such coils; and a pump connected with said lastnamed chamber for maintaining a vacuum therein.

8. In apparatus of the class described; the combination of two openevaporating pans; steam heating coils therein; an elevated vacuumchamber for each of said pans, each otsaid chambers having an ascendingpipe .for drawing the contents from the' corre-' sponding pan and adescending pipe for discharging separated crystals, the heating cons ofthe second pan being connected to receive steam from the, chambercorresponding with the first pan a connection be I tween such coils-andthe ascending-pipe of the chamber correspond ng with sa d second pan; avalve-controlled pipe adapted to con:

ncct the descending pipe of said last named chamber with such coils;another connection between such coils .and a receptacle. de-

pump connected with said lastlnamed chamber for maintaining a vacuumtherein.

9. In apparatus of the class described, the combination'of a seriesofopen heating yes- 7 sels; vacuum chambers respectively adapted toreceive the contents ot said vessels;

an'd'an exhausting device connected with the last of said .clunnbers formainta ning the desired degree ot' vacuum therein, said last chamberbeing connected with the remaining chambers in the series seassimultaneously to maintain a vacuum there n.

- Attcsted by- 10. In apparatus of the class described, the combinationof a series of open heating vessels; vacuum chambers respectivelyadapted to'receive the contents of said vessels; and an exhaustingdevice connected with the last of said ,-han'1bers for maintaining thedesired degree of vacuum therein, said last chamber being connected withthe remaining chambers in the series, the connections between saidchambers being so arranged and; constructed as siu'mltaneously tomaintain vacua therein but of lower degree in each succeeding chamber. I

llnIn apparatus of the class described, the combination with a series ofopen heating vessels having steam heating devices for said vessels; of acorre 'ponding series or vacuum chambers respectively connected toreceive the contents of said vessels; a pump connected to the last ofSand chambers and adapted to maintain the desired :lcgrce of vacuumtherein; of connections adapted to lead steam from each chamber. exceptthe last, to the next succeeding heating device and of connectionsbetween each chamber, except the first, and the heating devicecorresponding thereto, said last connections being. so arranged. andconstructed as to reduce in a predetermined manner the degree of vacuumin each succeeding chamber.

12. In apparatus of the c assdescribed, the combination of a series ofopen heating vessels ha-ving steam heating elements therein;'acorresponding series of vacliumchambers placed at serially increasingelevations respectively above the said vessels directly related thereto;connecting p'ipes adaptedto lead steam from each said chamber into theheating element of the said vessel directly related to the next higherchamber; an ex- 'liausting 1 device higher, chambgi connected tothe lastand and; adapted to maintain therein thedes'red degree of vacuum;circulat-ing pipes connecting the directly relatedchambers and vesselsrespectively'andf adapted to circulate, the contents of thelatter-through the former; watersealed drip pipes adapted to dischargethe water of condensation fronrthe heatingelements' when Working undervacuum;-and valve control led pipes connecting the respective heatingelements with the responding vessels as cally reduce the initial vacuumin the highest chamber to vacua of lower degree in eachsucceeding lower'chamber.

:nnnnnar it, now."

[ S-i'gnediby me this 25' day of November,

- Tno'sa G inswonn, E. O. B'Aas'row.

, directly related circulating pipes at such elevations above theircorthereby .toautomatt

